1. Field of the Invention
The present invention relates to an optical disc apparatus, such as an optical information recording and reproducing apparatus or optical information reproducing apparatus for recording information on an optical disc, such as a photo magnetic disc, and/or reproducing the recorded information. More precisely, the present invention relates to a galvanomirror unit incorporated in an optical system thereof.
2. Description of Related Art
In a known optical apparatus, an objective lens which converges a laser light beam from the laser source onto an optical disc and/or receives the light reflected from the optical disc, is linearly moved across the tracks of the optical disc in the radial direction. A known optical disc apparatus usually includes a galvanomirror unit for adjusting the laser beam emitted from the laser source within a vertical plane lying in the radial direction of the optical disc, parallel with the direction of movement of the objective lens. The galvanomirror unit has a galvanomirror which is rotated to vary the direction of the laser beam reflection with respect to the objective lens.
However, the conventional galvanomirror unit is incorporated in the optical system in a fixed manner, and accordingly, there is a possibility that the angular position of the galvanomirror reflecting surface might be improperly oriented, for example during assembly. To compensate for an improper initial angular position of the reflecting surface, it is necessary to provide an optical axis adjusting mirror separate from the galvanomirror unit.
However, the presence of an optical axis adjusting mirror, separate from the galvanomirror unit, increases the number of optical elements and results in a complicated optical arrangement.